Nut tapping machine



Dec. 14, 1943. GOLDBERG 2,336,478

NUT TAPPING MACHINE Filed March 15, 1940 15 Sheets-Sheet 1 v' y's Deg. 14, 1943. GOLDBERG 2,336,478

NUT TAPPING MACHINE Filed March 13, 1940 15 Sheets-Sheet 3 r V 4a 46- 9/ M0 9/ 15 Sheets-Sheet 4 Filed March 13, 1940 r. W 2 m u & W70

x z 6 1 U i j x I H Am I m i. Q Q I U I IL: w w rim W v ay fl O Z5 Dec. 14, 1943. H. GOLDBERG NUT TAPPI'NG MACHINE Filed March 13. 1940 15 Sheets-Sheet 5 Dec. 14, 1943.

H. GOLDBERG NUT TAPPING MACHINE Filed March 13, 1940 15 Sheets-Sheet 6 H. GOLDBERG- NUT TAPPING MACHINE Dec. 14, 1943.

Filed March 13, 1940 15 Sheets-Sheet 7 I I I r my 2 i a Z W 7 Dec. 14, 1943. H. GOLDBERG NUT TAPPING MACHINE 15 Sheets-Sheet 8 Filed March 13, 1940 Jim/67 1071 557777972 6 0 Zcfeiy Dec. 14, 1943. H. GOLDBERG NUT TAPPING MACHINE Filed March 13, 1940 l5 Sheets-Sheet 10 m7 ,7 f ga I K/I/Q 4/5 Dec. 14, 1943.

' H.'GOLDBE RG NUT @APPING MACHINE Filed March 13, 1940 15 Sheets-Sheet 11 Dec. 14, 1943. H. GOLDBERG NUT TAPPING MACHINE Filed March 13. 1940 15 Sheets-Sheet 12 4 67 77707? G0 76Ze/7 Dec. 14, 1943. GOLD ERG 2,336,471;

NUT 'I'APPING MACHINE Filed March 13, 1940 15 Sheefis-SheetlS Patented Dec. 14, 1943 UNITED STATES PATENT- OFFICE n $336,478: l f

NUT rarrma momma Herman Goldberg, Chicago, Ill. Application March 13, 1940, Serial No. 323,649

21 Claims. (01.10-136) This invention relates to improvements in maechines for tapping nut blanks or the like or, for performing other operations in which a rotating tool, or a plurality of tools, and. the work are brought into engagement, with each other, and its purpose is to provide a machine in which these operations are capable, of being rapidly and automatically repeated by fluid pressure means formed efliciently and with great. speed.

Machines of this general type have heretofore so that a continuous cycle of operations is peri been provided in which a relative movement has been eifeoted between a rotating ta'p or other not properly aligned with the tool. In the machine disclosed in said application, the movement of the work holder toward the operating tool is effected by fluid pressure and means are provided for regulating the speed and duration of the forward and return strokes of the work holder so that the work to be performed may be accomplished quickly and with accuracy whilifat the tool and 'adevice adapted to hold a nut'blank or other object to be worked upon, but 'most of these priornut tapping machines whichhave gone into'commercial use have been of the bentshank type in which the nut blanks to be tapped are fed over a tapping too1 having a bent shank, the tool being held by engagement with the surrounding nut blanks so'that it has been impossible to hold the tapping portionof the tool in a suihci'ently definite position to secure an accurate tapping of the nut blanks. There have been other commercial nut tapping machines in which the bent shank has not been employed, but these have been limited largely to use in tapping relatively large nuts and their speed of operation has been comparatively low. In some. of these prior machines resilient. means have been provided for permitting the too1-holding part or the work-holding part to yield and thereby pre vent injury to the tool or other parts in the event that the work is defective or is not properly positioned for engagement by the tool, but the speed of operation of most of these. prior machines has been limited and considerable pressure has been exerted upon the tap or other tool so that, when the work is defective or not properly positioned, the result has been that the tap or tool has deteriorated rapidly.

So far as applicant is aware, the only'exception to the types of nuttapping machines and the like referred to above, so far as commercial use is concerned, is to be found in the type of machine described and claimed in applicant's same time havingthe advantage that a continuous series of operations may be automatically carried on without attention on-the part of the operator except in initiating the cycle, While the machine of said application has many advantages over prior art machines intended for'like purposes, and has been found to be ver successful in commercial use, it has the disadvantage that it is limited to use with pieces of work of' relatively small size, such as nut blanks and the like, because of the fact that the work is moved toward and from the rotating ,tool and pieces of substantial size cannot be fed into position to be operated upon or moved toward and from the operating positionsin the manner followed in theoperation of that machine. v

The principal object of the'present invention is to overcome the limitations of the machine of said copending application and the deficiencies of the machines of the prior art referred to above by providing an improved machine adapted for use, in tapping nut blanks or-in performing other tapping and similar operations, wherein the nut blank or other work piece is held stationary while it is being operated upon and the rotating tap or other tool is movedtoward' and from the nut starting the cycle of operations. A further object of the invention is to provide an automatic co-pending application Serial No. 191,386, fi1ed- February '19, 1938, that machine being one in .which the holder for the nut blank or other work machine of this type in which the rotating tool is automatically moved toward and from the work along with automatic reversing mechanism for driving the tool so that the fluid pressure operated means which is employed for eflecting theforwardand reverse strokes of the tool" supporting and operating mechanism also performs the function of bringing about an automatic reversal of the direction of rotation of the tool at the proper points in each cycle of operations. Still another object of the invention is to provide an automatic machine tool capable of tapping nut blanks or performing other like operations and operated preferably by fluid pressure, wherein the fluid pressure is utilized for effecting a continuous series of forward and reverse strokes of.a rotating tool with respect to the nut blanks or other work pieces, and also to move these blanks or work pieces'to the position where they are engaged by the tool and for circulating a cooling fluid into contact with the work piece being operated upon and for performing other auxiliary operations which may be necessary to the efllcient operation of the machine. A particular advantage of the improved machine is that it embodies means for automatically regulating the length of stroke of the part by which the rotating tool is moved towardand from the work and also means for regulating the pressure with which the tool is brought into contact with the work, thus making it possible to adjust the machine to work pieces of varying sizes and also to regulate the pressure so that danger of injury to the rotating tool is overcome. Other objects relate to various features ofconstruction and arrangement of the improved machine which will appear more fully hereinafter.

The nature of-the invention will be understood from the following-specification taken with the accompanying drawings in which one example of a complete embodiment of the invention and certain modifications of parts thereof are illustrated. In the drawings,

Figure 1 shows a side elevation of one form of nut tapping machine embodying the features Fig. 5 is a partial vertical section taken on the line 5-5 of Fig. 2 showing the cylinder mechanism by which the tool is moved toward and from the work;

Fig. 6 shows an enlarged vertical section taken on the line 6-6 of Fig. 3;

Fig. 7 shows an enlarged horizontal section taken on the line I-I of Fig. 4;

Fig. 8 shows a horizontal section taken on the line 8-8 of Fig. 6;

Fig. 9 shows an enlarged horizontal section taken on the line 9-9 of Fig. 4;

Fig. 10 is a vertical section taken on the line Ill-l0 of Fig. 9 showing parts of the construction of the valve block and associated mechanism for controlling the fluid pressure opera ted means by which the movements of the tool toward and from the work are effected and controlled;

Fig. 11 shows a vertical section taken on the line lI-il of Fig. 10;

Fig. 12 is a vertical section taken on the line l2-i2 of Fig. 9;

Fig. 13 isa vertical. section taken on the line Fig. 14 is a vertical section taken on the line Fig. 15 is a horizontal section taken on the line l5-l5 of Fig. 12;

Fig. 16 is a horizontal section taken on the line l6-l6 of Fig. 12;

Fig. 17 is a horizontal section taken on the line l'l-l'l of Fig. 12;

Fig. 18 is a horizontal section taken on the line l8.-'i8 ofFig. 12;

Fig. 19 is a horizontal section taken on the line l9-l9 of Fig. 12;

Fig. 20 is a vertical section taken on the line 20-20 of Fig. 16;

Fig. 21 is a vertical section taken on the line 2l-2i of Fig. 9;

Fig. 22 is a vertical section taken on the line 22-22 of Fig. 9;

-Fig. 23 is a vertical section taken'on the 23-23 of Fig. 9;

Fig. 24 is a vertical section taken on the line 24-24 of Fig. 9;

Fig. 25 is a somewhat diagrammatic view of the principal operating parts of the machine with their fluid pressure connections showing the means by which fluid pressure is utilized for line controlling the forward and reverse strokes of the tool holder with respect to the work, for

controlling the pumping of the fluid to the work and for controlling the feeding of the work to the position where the work is engaged by the tool;

Fig. 26 shows an enlarged vertical section through the automatic reversing unit by whichthe direction of rotation of the rotating tool is changed automatically at certain points in the movement of the unit as a whole with respect to the work;

Fig. 27 shows a side elevation of the valve mechanism for controlling the admission of compressed fluid to the mechanism by which the movements 0 fthe tool holder and other operations are effected; f

Fig. 28 shows a rear elevation of the valve mechanism illustrated in Fig. 27;

Fig. 29 shows a top plan view of the mechanism illustrated in Fig. 28;

Fig. 30 shows a side elevation of the pedal which is employed by the operator to control the fluid pressure system, with a part of the pedal operated valve illustrated in vertical section;

Fig. 31 shows an enlarged vertical section through a pistontype pump capable of use in conjunction with the machine illustrated in the preceding flgures of the drawings for effecting the pumping of cooling fluid to the work being operated upon;

Fig. 32 shows a side elevation of a motor operated rotary'pump, partially in section, which may be employed in place of the pump illustrated in Fig. 31; v

Fig. 33 shows' a side elevation of the work holder shown in Fig. 1, part of the holder and feeding channel being shown in vertical section and the adjacent tapping tool being shown in elevation; v

Fig. 34 shows a top plan view of the work holder and feeding channel shown in Fig. 33;

Fig; 35 shows an end elevation of the parts illustrated in Fig. 34 with the work-feeding mechanism shown partly in vertical section;

Fig. 36 shows a partial side elevation similar to that.of Fig. 3 illustrating a modifled form of construction in which successive strokes of the tool holder are controlled by hand; and

Fig. 37shows a front elevation similar to that of the upper part of Fig. 2 of a modifled form of machine in which the fluid pressure operated mechanism is employed for eflecting the simultaneous operation of a plurality of tool holding and operating devices.

In Figs. 1 to 35, inclusive, of the drawings, the invention is illustrated as being embodied in a nut tapping machine which comprises an upright frame or housing 40 having an enlarged base portion 40a which is adapted to be secured to a floor or other support. This housing is provided on its front side with a vertically slotted guideway 4017 on which there is mounted a supporting bracket 4|a. of a work table 4| which is capable of being adjusted vertically by means of a worm and worm wheel operated by a crank 42 located at one side of the housing. The table is adapted to be secured in its adjusted position by a clamping screw operated by a handle 43. A work holder 44 is mounted on the table 4| to support the nut blanks or other pieces of work and, by the foregoing adjustment of the table, the pieces of work may be located in the proper position municates through branch pipes 54a, shown in Fig. 8, with passages 467, leading to the cylindershereinafter described for causing return strokes of the tool 45. From the valve. mechanism 50 an auxiliary compressed fluid line 65 leads downwardly to actuate the mechanismby which the pieces of work are fed in the work holder 44 to a position where they may be engaged by the rotating tool 45. As illustrated in Fig. 25, another compressed air line 66 leads from the valve mechanism 50 to theupper end of an oil pump 61 which may be thus actuated by compressed fluid for pumping oil from a well in the base portion 401'; of the housing 40 through a pipe 66 which leads through a valve 69 to a nozzle 10 adapted to discharge the cutting oil on the piece of work being engaged by the tool.

with respect to the rotating tap 45 or other tool which is actuated by the driving mechanism of 'mechanism 50, by which'the pressure platen 41 is moved vertically for the purpose of moving the tap 45 toward and from the work. The cylinder block 46 is mounted on the front face of the casing 40 beneath the overhanging part of a belt casing 5| which is secured to the upper end of the frame or housing 40 and which houses the belt and pulley connections by which the driving shaft of the reversible driving unit 46 is actuated from an electric motor 52. This electric motor is located with its shaft extending vertically in the upper part of the-housing 40 and its frame is secured to a plate or bracket 53 capable of being adjusted upon the upper end of the housing 40 for regulating the tightness of the belt or belts by which the reversible driving mechanism of the rotating tap is actuated from the motor.

' The feeding of the nut blanlm or other pieces of work to' the plates where they are engaged by the rotating tool 45 and the movements of the tool 45 toward and from the work are effected by the action of compressed air or other compressed fluid which may also be employed to effect the circulation of cutting oil or cooling fluid to the. rotating tool at the point where it engages the work. These fluid pressure connections are illustrated somewhat diagrammatically in Fig. where a supply pipe 55, leading from an air compressor or other source of compressed fluid, is shown as being connected to a pressure supply casing 56 from whichconnections extend to the cylinder block 48 and the valve mechanism 56. A pipe 51 leads from the casing 56 The electric conductors 13 for supplying electric current to the driving motor 52, and also to the pump motor 12, are led into the housing 46 at one side thereof, as -shown in Fig. 1. The s tch mechanism 14 for controlling the operation and the speed of the motor 52 is preferably mounted on the face of the housing 46 and this housing 46 also preferably encloses, as far as possible,

the various pipes by which compressed'air or other fluid is conveyed to and from the different parts of the fluid pressure operated mechanisms.

The foregoing description has been intended to give a general view of the principal parts of the machine and, inasmuch as this is a machine in which the nut blanks or other pieces of work through a pressure regulator 58 to a pressure platen 41 which moves the tool 45 toward the work. From the pressure chamber 56 a pipe 54, ileads through a pressure regulator 58a and a are held stationary and the rotating tool is moved toward and from them, the details of the means for holding the work pieces and for moving them into position will be described before entering upona detailed description of the other parts of the machine. As shown in Figs. 1, 2, 33, 34 and 35, the work holder 44 comprises a bracket 16 having base flanges 16a which are adapted to be clamped by studs 11 to the upper face of the work table 4|. siderable area so that it is adapted to receive the pieces of work which are discharged from the work holder and the table is provided around its edge with a channel 4|a adapted to collect the cutting oil which is discharged from the nozzle10 so that it may be conveyed through 16d. communicating with the. feed channel 16 and the blanks 18 are adapted to move by gravity from the hopper through the. feed channel 19 and through the branch channel 16d to the channel 16c where they are moved by fluid pressure mechanism from the tapping position occupied by the blank 18a to the position occupied by the gauge 59a-to the cylinder block 48 where it com- This table is of .con-

blank 18b. The blank 18b is retained against discharge from the channel 160 by a pawl 88 pressed by a spring 8| mounted in a recess in the wall of the channel 160, and each time that a new blank is fed to the tapping position 18a a tapped blank occupying the position 18b is forced out of the channel 180 against the compression of the spring 8| and then falls upon the table 4| or into any receptacle which may be provided for receiving it. In order to retain the blanks and the tapped nuts or other completed pieces of work within the channels 180 and 15d, guide plates 82 are secured to the head 18b of the work holder at the sides of these channels, these guide plates beingspaced upwardly from the head 18b by spacing sleeves 83 through which attaching screws 84 extend into the head of a nut blank occupying the position 18a, and the plunger is adapted to be actuated through a pin 86 which extends downwardly through a slot in the bottom of the head 16b where it is engaged by a piston 81 and also by a coil spring 88. The piston is adapted to effect a forward stroke of the plunger 85 and the coil'spring 88 is connected to the cylinder block 88, in which the piston 81 is mounted, so that it-effects a return stroke of the plunger 85 and also of the piston. The cylinder block 88 is attached to the underside of the enlarged head 18b of the work holder and the left hand end thereof, as viewed in Figs. 34 and 35, is connected through a coupling 88 with the auxiliary compressed air supply line:

85 previously described so that when compressed air is admitted to the pipe 85 through the valve mechanism 58, in a manner to be hereinafter described," the piston 81 is caused to move through a forward stroke, thus actuating the plunger 85 to move a tapped nut blank from the position 18a to the position 18b while at the same time discharging from the channel 18 a com- -pleted nut blank or other piece of work which has previously occupied the position 18b. The supply of compressed fluid being then automatically shut off, the spring 88 causes a return stroke of the plunger 85 and of the piston 86 and, at the end of that return stroke, a new nut blank or other piece of work18 moves from the branch channel 16d into the channel 180 in the working position 18a. In this way, nut blanks or other pieces of work are successively moved to the work position and successively discharged therefrom so that a number of pieces of work may be quickly, operated upon by the rotating tool 45.

The means for supporting and actuating the reversible driving mechanism, by which the rotating tool 45 is operated, is best illustrated in Figs. 1 to 8, inclusive, so far as the more eneral features are concerned. As there illustrated, the cylinder block 48 is shown as being secured to the upper front face of the housing 48 by means of two pairs of studs 8| which pass through aper- -tures formed in the block and through bosses a screw 83, as illustrated in Fig. 8. The cylinder block 48, which is thus rigidly attached to the upper part of the housing 48, is fitted on its upper side by the projecting part of the pulley casin 5| and the cylinder block is provided at its upper end with-an outward extension 48b adapted to engage the lower annular edge at the projecting part of the casing 5|.

The cylinder block is provided with a central bore opening through its upper end and havi mounted therein the hollow pulley shaft which is journaled in two sealed ball bearing units 86 fixed within the upper central bore 480 of the block, as shown in Figs. 5 and 6. The pulley shaft 85 has fixed upon the upper end thereof, within the casing 5|, a pulley 81 having a plurality of grooves 81a of different diameters formed therein and adapted to be engaged by the driving belt 88 which has a general V-shaped cross section adapted to fit in one of these grooves. The belt 88 is adapted to be driven by another pulley 88 fixed upon the rotor shaft of the driving motor 52. The pulley 88 is similar to the pulley 81, being provided with a plurality of grooves 88a of different diameters which are adapted to receive the belt 88. The two pulleys 81 and 88, each of which has a general cone-shaped form, are directed oppositely on their parallel shafts so that when the belt engages a groove of large diameter on one pulley it will simultaneously engage a groove. of similar diameter on the other, except when the belt is mounted on the intermediate grooves which may be ofsubstantially the same diameters. By shifting the belt 88 from one set of grooves to the other, a considerable range of the driving speed of the rotating tool 45 may be attained in addition to that which may be brought about by the adjustment of the speed of the motor 52. g

The hollow pulley shaft 85 is providedwith a plurality of longitudinal internal teeth adapted to form a splined engagement with the corresponding teeth formed on theupper end oi the driving shaft I88 which actuates the reversible driving mechanism 48 previously referred to. By means of this splined connection, the pulley shaft 85 is adapted to drive the shaft I88 in all positions of the platen 41 by which the rotating tool and the reversible driving unit are moved toward and from'the work. The upper end of the bore 480 is closed around the pulley shaft 85 by a cover plate |8| which secures in place an annular ring I82 adapted to overlap the upper ball bearing unit 88 and the lower end of the shaft 85 is threaded for engagement by a pair of lock nuts I83 which thus secure the pulley shaft against upward displacement. The cylinder block 48 has its central bore enlarged below the pulley shaft 85 as shown at 48d and this enlarged portion has secured therein a cylindrical bushing I84 which forms a bearing for the tubular bearing member 41a which is formed integrally with the intermediate portion of the pressure platen 41. The driving shaft I 88 extends through this tubular bearing member 41a and into the tubular bore 41b which is formed in the lower part of the pressure platen. At this point, the driving shaft I88 is connected to the reversible driving mechanism which is contained in the housing II8 havin an aperture II8a in the upper end thereof which is fitted by an annular flang 41c projecting from the lower face of the pressure platen.

The pressure platen 41, upon which the reversible driving mechanism is mounted, is actu- 41c previously referred to.

aseaera ated by fluid pressure for the purpose of moving the reversible driving unit and the rotating tool toward and from the work and, for this purpose, it is provided with lateral extensions 416., shown particularly in Figs. 6 and 7, which are apertured for engagement by the lower reduced extremities II 2a of piston rods II 2 which are adapted to be actuated by pistons I|3 secured thereto and mounted to slide within the cylindrical bores 48c of the cylinder block 48. Each of the cylinders 48a is closed at its lower end by a fixed cylinder head I I4 and at its upper end by a removable cylinder head H5 formed as a nut having the reduced part threadedly engaging the reduced threaded end of the cylinder. When the platen 41 is in its uppermost position, determined by the engagement of the central boss 41) thereof with the lower end of the cylinder block, as shown in Fig. 6, the pistons II3 are located slightly below the upper cylinder heads II5, so that compressed fluid may be admitted above these pistons to cause the downward stroke of the pressure platen 41 and a. corresponding downward movement of the reversible driving unit and the tool carried thereby. The cylinder block 4015 provided with chambers 489 in its upper part through which access may be had to the removable cylinder heads II5 when the cylinder block has been detached from the housing 40 or when the pulley casing 5| has been removed. The valve mechanism 50 and other parts by which compressed fluid is admitted to the cylinders 41 for causing the forward and reverse strokes of the platen 41 will be described after dealin urther with'the construction of the reversible driving mechanism.

The reversible driving mechanism is illustrated particularly in Fig. 26 where the shaft I00 is shown as having a tapered lower end I00a which flts within and has a splined engagement with the tapered bore of the hub portion IIGa of the hollow driving shell I IS. The hub portion of this driving shell is journaled in a sealed ball bearing unit I" which is secured in position against a shoulder at the upper end of the enlarged bore of the pressure platenby means of a ring nut I I8 engaging the internally threaded annular flange A pair of nuts I I I engage the threaded portion of the hub of the driving shell immediately above the ball bearing unit. The hub portion I lid of the driving shell has an annular horizontally extending shoulder IIIib seating against the lower face of the inner ring of the ball bearing unit I" and the driving shell is further provided with an integrally formed reverse driving gear II! which is arranged to mesh driving shell 6. The hub portion I a of the reverse driving shell is journaled in a hub portion lI0c of the housing IIO through a double ball bearing unit I 3i seated in the enlarged bore I I0d of the hub and, held in place by an annular plate I32 overlapping its upper end and attached to the hub portions of the housing by screws I33.

The annular friction clutch portions IIBb and I30b of the driving shell and the reverse driving shell, respectively, are constructed in the form of hollow truncated cones and have inner annular friction driving surfaces adapted .to be engaged alternately by the annular driving surfaces I350 and Ib, respectively, which are formed upon the inner driven shell or clutch member I35. This driven shell 'I35'is provided ,with an in- I wardly extending spider I350 which seats against a radially extending flange I 36a formed upon a sleeve I 36 secured by a transverse pin, I31 upon engage either the driving shell I It or the reverse with a pinion I20 formed upon the tubular member I2I which is Journ'aled by means of ball hearing units I22 upon acountershaft I23 secured within a lateral extension IIOb of the housing III. The tubular member I2I is secured upon the ball bearings I22 by split rings I24 and the shaft I23 is secured in place in its bearings by a set screw I25 The lower end of the member I2I has mounted'thereon or formed integrally therewith a gear I20 which meshes with an intermediate pinion I2I mounted to revolve on a stub shaft I 28 which is flxed in the lower hub portion IIOc of the housing II0 This intermediate pinion IZ'I meshes with a reverse driving gear I29 which is flxed upon the lower hub portion I300, of a reverse driving shell I 30. By this arrangement of gearing mechanism, the driving shell I30 driving shell I30 but it is adapted to be brought into engagement with one or the other'of these driving shells upon axial movement of the tap spindle I40. This spindle has its upper reduced extremity I40a joumaled in the. hub portion II6a of the driving shell through an intermediate ball bearing unit I4I held in place by an annular' ring I42 and the reduced portion I40a of the spindle is adapted to have longitudinal movement within this ball bearing unit to permit the necessary movement of the driven shell I35. At its lower end, the tap spindle I40 is journaled in a cylindrical sleeve I44 which is joumaled in the extremity of the hub portion I I0c of the housing IIO through an intermediate ball bearing unit I45. This ball bearing unit engages an annular shoulder on the hub atits upper'end and "is held in place by a ring nut I46 which threadedly engages the internally threaded lower extremity of the hub portion. The spindle I40 is adapted to slide vertically in the sleeve I44 to the extent necessary to bring the driven shell I35 into driving engagement with one or the other of the driving shells IIS and I30. The driven shell I35 is normally moved to the neutral position shown in Fig. 26 by a coil spring I41 which has one end mounted in a recess I44a formed in the upper end of the sleeve I44 and'the other end is. arranged to abut against an annular ring I40 secured to the spindle I 40 within the bore of the hub portion I30a of the reverse driving shell. This spring is so adjusted that when endwise pressure upon the spindle I40 is removed, the spindle is automatically returned to a position corresponding'to the neutral position of the driven shell I35. At its lower end the tap spindle I40 has secured thereon the longitudinally split collet I40 surrounded by the collet nut I50 which may be adjusted on the collet for the purpose of clamping therein the shank of the rotating tap or other tool 45 previously referred to.

It will be apparent from the foregoing description of the reversible driving mechanism-40 that when the pressure platen 41 is lowered to cause the tap 4-5 to engage a blank I8 held in the work is arranged to be driven continuously in a direcholder I3, the initial engagement of the tap with the blank will cause an upward movement of the 

